The sanctions, which ban the companies from doing business with the US government and US companies, were based on the Iran Non-Proliferation Act of 2000, which aims at preventing Teheran from developing nuclear weapons.

The United States has accused Iran of seeking to develop nuclear arms under the cover of its civilian nuclear energy program.

"These entities will be sanctioned based on credible information that they transferred equipments and technologies referred on the multilateral control lists to Iran," said State Department spokesman Adam Ereli.

"They are serial offenders," he added.

The companies hit were the public company China National Aero-Technology Import and Export Corporation (Catic), missile builder China North Industries Corp. (Norinco), the chemical equipment group Zibo Chemet Equipment Corp., Hongdu Aviation, Ounion International Economic and Technical Cooperative Ltd, Limmt Metallurgy and Minerals.

Two Indian chemical groups were also cited: Sabero Organics and Sandhya Organics.

Also cited was Austrian firearms maker Steyr-Mannlicher.

Ereli did not provide details on what the companies supplied to Iran, but stressed the credibility of the information on which Washington based the sanctions, which took effect December 23.

He noted that Norinco, a leading Chinese defense industry conglomerate, is a repeat offender.

He also praised the Austrian government for its cooperation in the case of Steyr-Mannlicher, suggesting as well that the sanctions on Steyr could be lifted quickly.

Some 40 companies have been sanctioned since the establishment of the Iran Non-Proliferation Act.

"It's an important and effective tool in constraining Iran's efforts to develop missile and WMD (weapons of mass destruction) capabilities," Ereli said.

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